Optimization of process variables in acid catalysed in situ transesterification of Hevea brasiliensis (rubber tree) seed oil into biodiesel

ABSTRACT

In situ transesterification of Hevea brasiliensis seed oil was done using sulphuric acid as catalyst with the aim of optimizing the process variables for higher yields. Response surface methodology based on Box-Behnken design was used to model the factors-yield relationship. The empirical model obtained shows that reaction time and amount of methanol are the most important variables that influence the process. Irrespective of the reaction temperature and concentration of the acid catalyst employed, biodiesel yields in excess of 80% are obtained only when the in situ transesterification is performed for >200 minutes when the volume of methanol is >9 cm³ per gram of the oilseed. The optimal process condition was discovered to be when the temperature, reaction time, amount of methanol and catalyst concentration are 55.91 °C, 240 minutes, 50.0 cm³, and 0.87 M, respectively. Validation results (93.15 ± 0.25%) are generally in agreement with the predicted value of 93.04%. Results from GC/MS analysis of the biodiesel revealed that the dominant components are methyl esters of linoleic and oleic acids (91%) while methyl esters of palmitic and stearic acids (9%) are the minor components of the biodiesel. Properties of the biodiesel showed that it was in conformity with ASTM D6751 requirement.

KEYWORDS:

• Hevea brasiliensis
• in situ transesterification
• biodiesel
• Box-Behnken design
• homogeneous catalysis

Acknowledgement

The second author would like to thank the Management of Shehu Shagari College of Education for granting her the fellowship for postgraduate studies.

Disclosure statement

No potential conflict of interest was reported by the authors.